Faculty Bibliography

Laser interstitial thermal therapy (LITT) has recently shown great promise as a treatment strategy for localized, focal, low-grade, organ-confined prostate cancer (CaP). Additionally, LITT is compatible with multi-parametric magnetic resonance imaging (MP-MRI) which in turn enables (1) high resolution, accurate localization of ablation zones on in vivo MP-MRI prior to LITT, and (2) real-time monitoring of temperature changes in vivo via MR thermometry during LITT. In spite of rapidly increasing interest in the use of LITT for treating low grade, focal CaP, very little is known about treatment-related changes following LITT. There is thus a clear need for studying post-LITT changes via MP-MRI and consequently to attempt to (1) quantitatively identify MP-MRI markers predictive of favorable treatment response and longer term patient outcome, and (2) identify which MP-MRI markers are most sensitive to post-LITT changes in the prostate. In this work, we present the first attempt at examining focal treatment-related changes on a per-voxel basis (high resolution) via quantitative evaluation of MR parameters pre- and post-LITT. A retrospective cohort of MP-MRI data comprising both pre- and post-LITT T2-weighted (T2w) and diffusion-weighted (DWI) acquisitions was considered, where DWI MRI yielded an Apparent Diffusion Co-efficient (ADC) map. A spatially constrained affine registration scheme was implemented to first bring T2w and ADC images into alignment within each of the pre- and post-LITT acquisitions, following which the pre- and post-LITT acquisitions were aligned. Pre- and post-LITT MR parameters (T2w intensity, ADC value) were then standardized to a uniform scale (to correct for intensity drift) and then quantified via the raw intensity values as well as via texture features derived from T2w MRI. In order to quantify imaging changes as a result of LITT, absolute differences were calculated between the normalized pre- and post-LITT MRI parameters. Quantitatively combining the ADC and T2w MRI parameters enabled construction of an integrated MP-MRI difference map that was highly indicative of changes specific to the LITT ablation zone. Preliminary quantitative comparison of the changes in different MR parameters indicated that T2w texture may be highly sensitive as well as specific in identifying changes within the ablation zone pre- and post-LITT. Visual evaluation of the differences in T2w texture features pre- and post-LITT also appeared to provide an indication of LITT-related effects such as edema. Our preliminary results thus indicate great potential for non-invasive MP-MRI imaging markers for determining focal treatment related changes, and hence long- and short-term patient outcome.

PURPOSE: Intracorporeal injections have low use rates and high discontinuation rates. We examined factors associated with intracorporeal injection use, long-term satisfaction with intracorporeal injection and reasons for discontinuation in men treated with radical prostatectomy. MATERIALS AND METHODS: Between October 2000 and September 2003, 731 men who underwent open radical retropubic prostatectomy were enrolled in a prospective outcomes study. The 8-year followup evaluation included the UCLA-PCI, and a survey capturing intracorporeal injection use, satisfaction and reasons for discontinuation. Logistic regression was used to determine associations between intracorporeal injection use and preoperative variables. RESULTS: The 8-year self-assessment was completed by 368 (50.4%) men. Of these men 140 (38%) indicated prior or current intracorporeal injection use, with only 34 using intracorporeal injection at 8 years. Overall, 44% of the men were satisfied with intracorporeal injections. Reasons for discontinuation included dislike (47%), pain (33%), return of erection (19%), inefficacy (14%) and no partner (6%). Men trying intracorporeal injections had greater preoperative UCLA-PCI sexual function scores (75.2 vs 65.62, p = 0.00005) as well as greater decreases in this score at 3 months (p = 0.0002) and 2 years (p = 0.003). Higher preoperative sexual function scores were independently associated with the use of intracorporeal injections in a model adjusted for age, marital status, nerve sparing status and body mass index (OR 1.021, 95% CI 1.008-1.035). CONCLUSIONS: Men pursuing intracorporeal injections have better baseline erectile function and experience greater deterioration in erectile function during the early postoperative period. Despite the high efficacy of injections, many men discontinue intracorporeal injections due to dislike or discomfort. Satisfaction rates for intracorporeal injections indicate their long-term role in restoring sexual function in men with post-prostatectomy erectile dysfunction.